Do Speed Limits Actually Keep Us Safer?

Jul 17, 2018

Do Speed Limits Actually Keep Us Safer?

Posted By
Fitzpatrick Mariano Santos Sousa P.C.

It seems like a headline we see all too often: a motorist was killed as
result of a high-speed crash while flying down the road at insane speeds.
It’s incidents like this that bring law enforcement, politicians,
community safety groups, and car insurance companies out to all say the
same message: speed kills. They also use this as justification for speed
limits on our local roads, slowing drivers down at the risk of an expensive
traffic ticket.

However, several studies have shown that speed limits may not actually
be keeping us safer in some instances. On this blog, we’ll take
a look at how they’re actually
increasing the risk of an accident in some situations.

Drivers Choose a Safe Speed

Have you ever noticed that you’re driving along the road and the
flow of traffic is doing a speed that’s five, ten, or even 15 to
20 miles per hour
faster than the posted speed limit? This is actually a fairly common phenomenon,
and it’s demonstrated by what’s known as the “Solomon
Curve.” The Solomon curve essentially states that the overwhelming
majority of drivers will choose a speed that’s safe and appropriate
for the conditions of a given road, regardless of what the posted speed limit is.

For example, drivers in a school zone or commercial business district with
a lot of crosswalks, busy sidewalks, and cars parked along the side of
the road will usually choose a speed of around 25 to 35 miles per hour:
the safest they can navigate on a road of that type. However, on a multi-lane
divided highway with no traffic signals or stop signs, such as a freeway,
drivers will usually choose speeds around 70 to 75 miles per hour.

Speed Limits & The Solomon Curve

The Solomon Curve indicates that the speed that approximately 85 percent
of drivers choose is safe and appropriate, and presents the least chance
of an accident. However, there are lots of times when the posted speed
limit is actually below the Solomon Curve sweet-spot. When this is the
case, there will always be a percentage of drivers who try to be good
sports about the law and follow it (as we said, speeding tickets are expensive,
as is car insurance). However, when these people are driving five, ten
or even 15+ miles per hour
slower than the flow of traffic, they become a serious safety risk to those around them.

Look at it this way: you’re cruising down a wide-open multi-lane
divided highway at a comfortable speed of 65 miles per hour. The majority
of cars around you are doing roughly the same speed, with about a two
or three mile per hour difference. However, the posted speed limit is
just 50 miles per hour, and you come up to a car who is doing 45 to stay
safely under the limit. At this point, not only do you have to slam on
your brakes to avoid hitting that driver, but then you have to worry about
changing lanes to get around them. This immediately becomes an extremely
dangerous situation: not only do you have to worry about other drivers
behind you having to slow down to avoid hitting you, but you also need
to figure out how to safely change lanes to get around them. When you
have a difference of 20 miles per hour between yourself and the rest of
the flow of traffic, that becomes an immensely dangerous maneuver that
requires several hundred feet of space between you and the next driver back.

If the road is busy, you may not necessarily get the perfect opportunity,
so you’ll try to jump in where you can and jam on the gas to try
and get up to speed again quickly, but by that point the driver behind
you may have to slow down, causing the drivers behind them to have to
pay attention and slow down, and thus, you get a domino effect of accident
risk behind you, all because of one driver going way slower than the flow
of traffic.

How to Improve Safety

Several studies have shown that increasing speed limits on these roads
will not only encourage people to drive safer, but even decrease accident risks.
A study conducted in 1997, known as the “Parker” study, chose 100 sites across the country and either raised or lowered the speed
limit slightly and calculated the effects the changes had on accident
rates. The results were exactly the opposite of what we hear from so many
people: the areas with increased speed limits saw a decline accidents,
while the areas with the lower limits actually saw more accidents than
before. This is because the areas with higher limits saw fewer motorists
driving at speeds that interfered with the flow of traffic.

That doesn’t mean drivers who drive recklessly fast shouldn’t
be cited and pulled off the road—speed limits do have a purpose.
However, speed limits that are too low create speed variance, and speed
variance is one of the leading causes of speed-related car accidents.
As such, if authorities really wanted to keep people safe, they’d
make fewer speed traps (roads with unnecessarily low speed limits) and
increase the limits on roads that can safely handle higher speeds to encourage
more drivers to move at reasonable speeds.